The rapid progress of LED technology in the 1990s not only exceeded the luminous efficiency of incandescent lamps, and the light intensity reached the candlelight level, but the colors also covered the entire visible spectrum from red to blue. This technological revolution from indicator level to beyond the level of general light sources has led to a variety of new applications, such as car signal lights, traffic lights, large outdoor full-color display screens, and special lighting sources.
With the development of high-brightness and multi-color light-emitting diodes, the application field is also expanding. From the lower luminous flux indicator to the display screen, and then from the outdoor display to the medium luminous flux power signal lamp and the white light source for special lighting, finally Developed to the upper right corner of the high luminous flux general lighting source. The year 2000 is the dividing line of time. In 2000, the signal display problems and lighting problems of all colors have been solved, and special lighting applications with low and medium luminous fluxes have begun. However, as general lighting applications for high luminous flux white light lighting, it seems that there is still time. In Japan, the luminous flux needs to be further increased significantly before it can be realized. Of course, this is also a process, which will be gradually realized as the brightness increases and the price decreases.
LED display
Since the mid-1980s, there have been monochrome and multi-color display screens, initially text screens or animated screens. In the early 1990s, the development of electronic computer technology and integrated circuit technology enabled the realization of the video technology of LED display screens. TV images were directly displayed on the screen. Especially in the mid-1990s, blue and green ultra-high-brightness LEDs were successfully developed and put into production quickly. Greatly expand the application of outdoor screens, with an area ranging from 100 to 300m.
At present, LED displays have been widely used in stadiums, squares, venues, and even streets and shopping malls. The Nasdaq full-color screen on Times Square in the United States is the most famous. The screen area is 120 feet × 90 feet, which is equivalent to 1005m. Made of 10,000 ultra-bright blue, green and red LEDs. In addition, securities market screens, bank exchange rate screens, and interest rate screens also account for a large proportion of applications. Recently, there has also been a significant development in information screens on expressways and elevated roads. The application of light-emitting diodes in this field has become a scale, forming a new industry, and a relatively stable growth can be expected.
traffic light
The beacon light has been using LED as the light source for many years, and the current work is to improve and perfect. Road traffic signal lights have made great progress in recent years. The technology has developed rapidly and the application has developed rapidly. China currently has about 40,000 sets of orders per year, and California, the United States, replaced 50,000 sets of traditional LED traffic lights in the past year. According to the use effect, the signal lamp of the light source has a long life, power saving and maintenance-free effect. The current peak wavelengths of LEDs used are red 630nm, yellow 590nm, and green 505nm. It should be noted that the driving current should not be too large, otherwise the high temperature conditions under the summer sun will affect the life of the LED.
Recently, LED airport-specific signal lights used in airports as beacons, floodlights and omnidirectional lights have also been successful and put into use, with good results from many parties. It has independent intellectual property rights and has obtained two patents . It has good reliability, energy saving, maintenance-free, and can be promoted and applied to various airports. It can replace old signal lights that have been used for decades. It not only has high brightness, but also because of the purity of LED light color Good, very clear, easy to identify the signal.
Car lights
Ultra-bright LED can be made into car brake lights, tail lights and direction lights, and can also be used for instrument lighting and interior lighting. It has obvious advantages over incandescent lamps in terms of vibration resistance, power saving and long life. Used as a brake light, its response time is 60ns, which is much shorter than the 140ms of an incandescent lamp . Driving on a typical highway will increase the safety distance of 4-6m.
LCD backlight
As the backlight source of liquid crystal display, LED can not only be used as green, red, blue, and white, but also as a color-changing backlight. Many products have entered the stage of production and application. Recently, the LCD screen on the mobile phone uses LED to make the backlight, which has improved the grade of the product, and the effect is very good. The 15-inch (1 inch ≈ 2.5 cm) LCD screen backlight made of 8 blue, 24 green, and 32 red Luxeon LEDs can reach 120W, 2500 lm, and brightness 18000nits (nits, cd/m²). 22 LCD screen backlight has also been made, only 6mm thick, not only has a good color mixing effect, but also has a color rendering index of more than 80. Although large-scale backlights are currently in the development stage, they have great potential.
Lighting
Due to the increase in the brightness of light-emitting diodes and the decrease in prices, coupled with long life, power saving, simpler drive and control than neon lights, not only can flash, but also change color, so the monochromatic, multi-color and even color made of ultra-high-brightness LED The color-changing light-emitting columns are equipped with light-emitting units of other shapes and colors to decorate tall buildings, bridges, streets and squares and other landscape projects with great effect, presenting a scene of colorful, star-flickering and colorful streamers. Many companies have produced LED beams of more than 10,000 meters and tens of thousands of colored lights. They are currently being gradually promoted, and it is estimated that they will gradually expand to form a single industry.
Lighting source
As the lighting source, the LED light source should be white light. At present, as military white light LED lighting lamps, some varieties have been put into mass production. Since the LED light source has no infrared radiation, it is easy to conceal, and it also has the advantages of vibration resistance, suitable for battery power supply, solid structure and convenient carrying, etc., there will be greater development in special lighting sources. Lawn lamps and underground lamps for civilian use have been produced on a large scale, and they are also used as microscope field lighting, flashlights, surgeons' headlights, museums or art exhibitions, and reading lamps.
Greenhouse supplement light
Light is one of the most important environmental factors for plant growth and development. It has a regulatory effect on plant growth and development, morphogenesis, photosynthesis , material metabolism and gene expression . Therefore, greenhouse light supplementation is an important way to achieve high-quality and high-yield plants. In recent years, the application of light-emitting diodes in plant factories has become more and more extensive. The advantages of LED light source's narrow wave width, low energy consumption, small size, high efficiency, aging resistance, and low heat consumption have made it a lot of light quality researchers. New light source used. So far, a large number of LED light sources have been used to study the effects of light environment on the macroscopic morphology, yield, and quality of plants , as well as the effects on cell microstructure, plant differentiation, and secondary metabolites .
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